Tempo-controller for automatic pianos.



A. H. STUART. TEMPO OONTROLLER FOR AUTOMATIC PIANOS.

APPLICATION FILED APR.5,1909.

962,537., Patented June 28, 1910.

2 SHEETS-SHEET 1.

T n 3 2 1, \wTr Inventor r 4mm? If. 572 45? APPLIGATION FILED/APR. a,1909.

0 0 1 3 4 w 7 m M MW 6 5 6A 6 6T U mm T E J3 6 5 r as 6" s 0 a m 5 H w mr P w W AMV m H M w I w I A 4 U m ALBERT H. STUART, OF BOSTON,MASSACHUSETTS.

TEMPO-CONTROLLER FOR AUTOMATIC PIANOS.

Specification of Letters Patent.

Patented June 28, 1910.

Application filed April 5, 1909. Serial No. 488,087.

To all whom it may concern:

Be it known that I, ALBERT H. STUART, of Boston, in the county ofSuffolk and State of Massachusetts, have invented certain new and usefulImprovements in Tempo-Controllers for Automatic Pianos, of which thefollowing is a specification.

This invention relates to automatic pianos and has for its object toprovide means for automatically controlling the tempo so as tocompensate for variations in the speed of the main exhaust pump.

An automatic piano includes in its organization a tracker board and atraveling perforated sheet cooperative with the tracker board forcontrolling the hammers. It also includes winding rolls for theperforated sheet, a pneumatic motor for the winding rolls, and anexhaust pump connected with the motor by a conduit for driving themotor. The exhaust pump is usually actuaated by pedal levers and may beactuated at any desired speed at the will of the operator. There isusually included in the conduit between the exhaust pump and the motor atempo valve adapted to be operated by a hand lever for controlling theflow of air to the exhaust pump, and thereby controlling the speed ofthe motor and the speed of the perforated sheet. The motor however, issubject to variations in speed when the tempo valve remains in oneposition and when the speed of the exhaust pump is varied. WVithout someautomatic means for compensating for variations in speed of the pump,the motor is bound to operate unevenly.

A patent issued April 19, 1892, No. 473,338 and a patent issued May 19,1896, No. 560,303 include pneumatic controllers for automaticallycontrolling the speed of the motor of an automatic piano. In each ofsaid patents the controlling valve is of a sliding type, and cooperateswith a partition having a circular port or wind passage. The valves inthese patents require lubrication to facilitate their movement, but thelubrication becomes worn away in time and the valves which are forcedagainst their seats by the vacuum frequently stick. Cli matic changesare another cause for the sticking of these valves. The presentinvention provides a valve which is similar in effect to the slidingvalves of said patents. The valve of the present invention, however, isso constructed and. arranged as to avoid the objection due to stickingor binding. The sticking or binding of the valve is avoided by formingthe valve so that it may enter the port or wind passage and by mountingit directly upon the movable leaf of the controlling pneumatic, and byarranging the pneumatic so that the valve is moved longitudinally intoand out of the port or wind passage. The valve does not have physicalcontact with the member in which the port or wind passage is formedbecause the circular diameter is slightly less than the diameter of theport, and the valve is arranged so that it may have a slight clearanceat all points. The automatic valve is provided in addition to, and notby way of substitution for, the usual tempo valve which may be actuatedmanually for increasing or diminishing the capacity of the air conduit.

I have found the most successful means for automatically controlling theflow of air to be a valve formed with a controlling face which isoblique to the direction of movement, and of which the width de creasestoward the rear. The cross section of the valve may be circular orpolygonal, and if it be the latter the decreasing width of thecontrolling face is procured by arranging said face so that itterminates coincidentally with an angle of the cross-section. The meansshown for moving the valve comprise a pneumatic included in the exhaustconduit between the motor and the manual tempo-valve and which has aport formed in one leaf and which has a valve mounted on the other leafso as to be adapted to enter the port.

Of the drawings which illustrate one form in which the invention may beembodied, Figure 1 represents in vertical section, the essential partsof a piano case and the several operative parts of an automatic playerto which this invention relates. Fig. 2 is a section on line 2-2 ofFig. 1. Fig. 3 is a section on line 33 of Fig. 2. Fig. 4 is a section online 4-& of Fig. 3. Figs. 5, 6, 7 and 8 are perspective views of variousforms of controlling valves.

The same reference characters indicate the same parts wherever theyoccur.

Fig. 1 shows a piano case 10 having a floor 11, an upper front panel 12,and a lower front panel 13. Inclosed within the case is a frame 14. inwhich are mounted a tracker board 15 and a pair of winding rolls 16, oneon either side of the tracker board. 17 represents a perforated musicsheet adapted to cooperate with the tracker board and to be wound uponthe rolls 16. 18 is a conventional representation of a pneumatic motorfor driving the winding rolls and is presumably equipped withappropriate power transmitting mechanism not shown. 20 represents anexhaust pump of the bellows type which is adapted to be actuated by apedal lever 21. It is the usual practice to provide two bellows 20 and aseparate pedal 21 for each. The pedals are mounted upon a fulcrum 22 andare connected by pivoted links 23 with arms 24 depending from themovable leaves 25 of the bellows. The bellows may be provided withsprings 26 arranged so as to exert their tension, tending to close them,the opening of the bellows being effected by a downward pressure uponthe pedals.

The exhaust pump, including the two bellows, is connected with the motor18 by a continuous air conduit which, as here shown, comprises anexhaust chest 27, a pneumatic 28, a pipe 29 connecting the motor 18 andthe pneumatic, and pipes 30, 30 one connecting each of the bellows 20with the exhaust chest 27 as shown by Figs. 3 and 4. The exhaust chest27 is divided by a partition 31 into two chambers 32 and 33. A port 34provides communication bet-ween the interior of the pneumatic 28 and thechamber 32 and is opened and closed as hereinafter explained for thepurpose of automatically controlling the flow of air from the motor tothe exhaust pump. The partition 31 is provided with a triangular opening35, (see Fig. 2) which is adapted to beregulated by a sliding plate 36usually called a tempo valve. The means here shown for regulating thetempo valve includes a stem 37, a hand lever 38, a rock shaft 39 affixedto the hand lever, an arm 40 aifixed to the rear end of the rock shaft,a swinging arm 41 mounted upon a fulcrum 42, a pivoted link 43connecting the arms 40 and 41, and a pivoted link 44 connecting the arm41 with the stem 37. It is not to be understood that the tempo valvehere shown and its actuating mechanism form any part of the presentinvention. The air conduit may be traced from the motor 18 through thepipe 29 into the pneumatic 28, through the port 34, chamber 32, port 35,chamber 33 and either one of the branchpipes 30 together with theirrespective bellows. The air is exhausted from the bellows through ports45 which are normally covered by clappers' 46. The supply for theexhaust pump is presumably taken from the atmosphere through the motor18.

The essential features of the present invention .are embodied in thepneumatic 28' and the several parts associated therewith and hereinafterdescribed. The pneumatic 28 includes a movable leaf 47 and a leaf spring48 tending to move the leaf 47 to open position. The spring 48 comprisestwo leaves fastened together at 49 and provided with a slide 51embracing both leaves and adapted to bemoved toward and from the point49 for varying the tension of the spring. On the movable leaf 47 of thepneumatic is affixed a beveled valve 50 whose oblique face is arrangedto cooperate with the port 34 connecting the pneumatic and the exhaustchest 27. In the drawings, the pneumatic is shown in open position inwhich the valve 50 is entirely withdrawn from the port 34. v

The operation for automatically controlling the flow of air to theexhaust pump is as follows :For example supposing the pedal levers areactuated so fast as to cause the exhaust pump to draw through the airconduit a greater supply of air than the amount which may readily passthrough the tempo valve opening 35. This causes an excessive vacuum inthe chamber 32 of the exhaust chest. .11 corresponding vacuum exists inthe pneumatic 28 which is thereby compressed so as to cause the movableleaf 47 to move toward the port 34. The smaller end of the valve 50enters the port 34 thereby restricting the air conduit at that point andcompensating for the excessive vacuum developed by the pump. On theother hand, if the movements ofthe exhaust pump should diminish, thevacuum in the pneumatic 28 would decrease, thus enabling the spring 48to move the leaf 47 to open position and thus provide a greater openingin the air conduit at the port 34. It will thus the motive force in themotor 18 was in each case the product of the flow and pressure which,when so combined, give substantially the, same motive force under allconditions.

The valve 50 which is included in Figs. 3 and 4 is perhaps the simplestand least expensive, and is produced from a cylindrical plug outobliquely so as to leave'an, oblique face 50'. The fact that the plug iscircular in cross-section and that, the face 50 is oblique results inthe shape or outline given said face in Fig. 4. The face isapproximately pointed at its forward and rear extremes and its greatestwidth is midway between said extremes. When the pointed end I of thevalve is inserted in'a circular port such as that indicated at '34, theinitial and terminal rates of change in the degrees of cut-off arerelatively slight and the rate of change when the controlling face isone-half within and one-half without the port is maximum.

It may in some cases be found desirable to provide a valve whose initialrate of change is minimum and Whose rate of change in proportion tosuccessive increments of movement shall increase through its entiremovement. A valve adapted to give the latter result is shown by Fig. 5,in which the controlling portion of the Valve indicated at 150 isconical.

The valve shown by Fig. 6 and indicated at 60 is rectangular in crosssection and its controlling portion is formed with diverging controllingfaces 61, which give the valve a shape similar to that of a chisel. Theeffect produced by the valve 60 is uniform with regard to the rate ofcut-01f.

Fig. 7 shows a valve 70 which is rectangular in cross section and whichis formed with converging controlling faces 71. The effect of the valve70 is uniform like that of the valve 60. The valve 80 shown by Fig. 8 islikewise rectangular in cross section but has a single cont-rolling faceindicated at 81. The face 81 is oblique to the line of travel and itseffect is a uniform rate of change in cut-off.

It is to be understood that the valve of whatever cross-section it maybe is intended to be employed in connection with a port of similar crosssection. The forms here shown illustrate only a few of the shapes whichmay be employed and it will be understood that other shapes are withinthe and out of said port, said valve having an operative face which isoblique to its line of travel and which increases in width from itsfront and rear extremes toward the intermediate portion.

2. In an automatic piano, a pneumatic motor, an exhaust pump and conduitcommunicating therewith, said conduit including a pneumatic and a portopening into the pneumatic, and a valve mounted on the movable wall ofthe pneumatic so as to move endwise in and out of said port, said valvehaving a controlling surface inclined to the line of travel and formedof graduated width narrower toward the ends and broader between theends.

3. In an automatic piano, a pneumatic motor, an exhaust pump and conduitcommunicating therewith, said conduit including a port, and a valvemovable endwise in and out of said port, said valve having an operativeface which is oblique to the line of travel, and of which the side edgesconverge toward the rear end.

In testimony whereof I have aflixed my signature, in presence of twowitnesses.

ALBERT H. STUART.

Witnesses:

E. BATOHELDER, W. P. ABELL.

